1. Field
The present invention relates to electrical machines, and more particularly, to brushless electric motors.
2. Background
Generally a brushless motor includes a rotor having a shaft with a permanent magnet affixed thereto. The brushless motor may also include a stator having a hollow cylinder with ball bearing mounted on an interior portion of the cylinder to rotatably support the rotor shaft. The stator may also include induction coil windings mounted on the case of the motor or interleaved with laminated iron rings. Current may be applied to the stator windings to cause the magnet to rotate and thereby deliver rotary power to the rotor shaft.
Although brushless motors generally can be made to spin faster and handle higher currents than brush motors, they have disadvantages associated with variations in the magnetic flux field at the magnets and the laminations that comprise the magnetic return path, which may cause cogging and concomitant vibration in the motor and associated structures as well as energy losses in the laminations due to induced eddy currents. Slotless brushless DC motors may exhibit reduced cogging but may require that the wires comprising the stator be supported by a fixed laminate structure thus having reduced energy conversion efficiency due to induced eddy current losses. Energy losses due to heating of the laminate structures found in brushless motors may negatively impact the efficiency of the motor and total power output. There is therefore a need in the art for improvements in brushless motor design.